Top: strengths (Q_m and total Q_T) of the m = 1 to m = 4 Fourier components of the stellar potential within the central kiloparsec. The m = 1 term is dominant up to a radius of 200 pc, and after the m = 2 component dominates and has a constant phase, corresponding to the bar. Bottom: corresponding phases in radians of the Fourier components, taken from the major axis, in the deprojected image.